service/dconf-gvdb-utils.c

   1 /*
   2  * Copyright © 2010 Codethink Limited
   3  * Copyright © 2012 Canonical Limited
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the licence, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Ryan Lortie <desrt@desrt.ca>
  19  */
  20
  21 #include "config.h"
  22
  23 #include "dconf-gvdb-utils.h"
  24
  25 #include "../common/dconf-paths.h"
  26 #include "../gvdb/gvdb-builder.h"
  27 #include "../gvdb/gvdb-reader.h"
  28
  29 #include <errno.h>
  30 #include <glib.h>
  31 #include <glib/gstdio.h>
  32 #include <string.h>
  33
  34 DConfChangeset *
  35 dconf_gvdb_utils_read_and_back_up_file (const gchar  *filename,
  36                                         gboolean     *file_missing,
  37                                         GError      **error)
  38 {
  39   DConfChangeset *database;
  40   GError *my_error = NULL;
  41   GvdbTable *table = NULL;
  42   gchar *contents;
  43   gsize size;
  44
  45   if (g_file_get_contents (filename, &contents, &size, &my_error))
  46     {
  47       GBytes *bytes;
  48
  49       bytes = g_bytes_new_take (contents, size);
  50       table = gvdb_table_new_from_bytes (bytes, FALSE, &my_error);
  51       g_bytes_unref (bytes);
  52     }
  53
  54   /* It is perfectly fine if the file does not exist -- then it's
  55    * just empty.
  56    */
  57   if (g_error_matches (my_error, G_FILE_ERROR, G_FILE_ERROR_NOENT))
  58     g_clear_error (&my_error);
  59
  60   /* Otherwise, we should report errors to prevent ourselves from
  61    * overwriting the database in other situations...
  62    */
  63   if (g_error_matches (my_error, G_FILE_ERROR, G_FILE_ERROR_INVAL))
  64     {
  65       /* Move the database to a backup file, warn and continue with a new
  66        * database. The alternative is erroring out and exiting the daemon,
  67        * which leaves the user’s session essentially unusable.
  68        *
  69        * The code to find an unused backup filename is racy, but this is an
  70        * error handling path. Who cares. */
  71       g_autofree gchar *backup_filename = NULL;
  72       guint i;
  73
  74       for (i = 0;
  75            i < G_MAXUINT &&
  76            (backup_filename == NULL || g_file_test (backup_filename, G_FILE_TEST_EXISTS));
  77            i++)
  78         {
  79           g_free (backup_filename);
  80           backup_filename = g_strdup_printf ("%s~%u", filename, i);
  81         }
  82
  83       if (g_rename (filename, backup_filename) != 0)
  84         g_warning ("Error renaming corrupt database from ‘%s’ to ‘%s’: %s",
  85                    filename, backup_filename, g_strerror (errno));
  86       else
  87         g_warning ("Database ‘%s’ was corrupt: moved it to ‘%s’ and created an empty replacement",
  88                    filename, backup_filename);
  89
  90       g_clear_error (&my_error);
  91     }
  92   else if (my_error)
  93     {
  94       g_propagate_prefixed_error (error, my_error, "Cannot open dconf database: ");
  95       return NULL;
  96     }
  97
  98   /* Only allocate once we know we are in a non-error situation */
  99   database = dconf_changeset_new_database (NULL);
 100
 101   /* Fill the table up with the initial state */
 102   if (table != NULL)
 103     {
 104       gchar **names;
 105       gint n_names;
 106       gint i;
 107
 108       names = gvdb_table_get_names (table, &n_names);
 109       for (i = 0; i < n_names; i++)
 110         {
 111           if (dconf_is_key (names[i], NULL))
 112             {
 113               GVariant *value;
 114
 115               value = gvdb_table_get_value (table, names[i]);
 116
 117               if (value != NULL)
 118                 {
 119                   dconf_changeset_set (database, names[i], value);
 120                   g_variant_unref (value);
 121                 }
 122             }
 123
 124           g_free (names[i]);
 125         }
 126
 127       gvdb_table_free (table);
 128       g_free (names);
 129     }
 130
 131   if (file_missing)
 132     *file_missing = (table == NULL);
 133
 134   return database;
 135 }
 136
 137 static GvdbItem *
 138 dconf_gvdb_utils_get_parent (GHashTable  *table,
 139                              const gchar *key)
 140 {
 141   GvdbItem *grandparent, *parent;
 142   gchar *parent_name;
 143   gint len;
 144
 145   if (g_str_equal (key, "/"))
 146     return NULL;
 147
 148   len = strlen (key);
 149   if (key[len - 1] == '/')
 150     len--;
 151
 152   while (key[len - 1] != '/')
 153     len--;
 154
 155   parent_name = g_strndup (key, len);
 156   parent = g_hash_table_lookup (table, parent_name);
 157
 158   if (parent == NULL)
 159     {
 160       parent = gvdb_hash_table_insert (table, parent_name);
 161
 162       grandparent = dconf_gvdb_utils_get_parent (table, parent_name);
 163
 164       if (grandparent != NULL)
 165         gvdb_item_set_parent (parent, grandparent);
 166     }
 167
 168   g_free (parent_name);
 169
 170   return parent;
 171 }
 172
 173 static gboolean
 174 dconf_gvdb_utils_add_key (const gchar *path,
 175                           GVariant    *value,
 176                           gpointer     user_data)
 177 {
 178   GHashTable *gvdb = user_data;
 179   GvdbItem *item;
 180
 181   g_assert (g_hash_table_lookup (gvdb, path) == NULL);
 182   item = gvdb_hash_table_insert (gvdb, path);
 183   gvdb_item_set_parent (item, dconf_gvdb_utils_get_parent (gvdb, path));
 184   gvdb_item_set_value (item, value);
 185
 186   return TRUE;
 187 }
 188
 189 gboolean
 190 dconf_gvdb_utils_write_file (const gchar     *filename,
 191                              DConfChangeset  *database,
 192                              GError         **error)
 193 {
 194   GHashTable *gvdb;
 195   gboolean success;
 196
 197   gvdb = gvdb_hash_table_new (NULL, NULL);
 198   dconf_changeset_all (database, dconf_gvdb_utils_add_key, gvdb);
 199   success = gvdb_table_write_contents (gvdb, filename, FALSE, error);
 200
 201   if (!success)
 202     {
 203       gchar *dirname;
 204
 205       /* Maybe it failed because the directory doesn't exist.  Try
 206        * again, after mkdir().
 207        */
 208       dirname = g_path_get_dirname (filename);
 209       g_mkdir_with_parents (dirname, 0700);
 210       g_free (dirname);
 211
 212       g_clear_error (error);
 213       success = gvdb_table_write_contents (gvdb, filename, FALSE, error);
 214     }
 215
 216   g_hash_table_unref (gvdb);
 217
 218   return success;
 219 }